For a method for restricting users of office automation equipment, such as a personal computer and complex equipment, and operational equipment such as a POS terminal and credit-service terminal, there are known a method of performing user authentication using a user specific ID and a password and a method of performing user authentication using biometrics information of a user. Recently, a method of restricting users by using an RFID is also known.
There is disclosed in Japanese patent publication No. 2931276 a user restricting system including an ID signal transmission unit and a use restriction release unit. Each of the users of the system carries an ID signal transmission unit, that is an aspect of an RFID module, and the use restriction release unit is provided in a device to which such user restriction is applied.
The ID signal transmission unit, provided with a transmitter and a receiver, transmits an ID code signal (ID) at a constant intensity. The use restriction release unit, also provided with a transmitter and a receiver, sends to the relative device a signal that releases the restriction of the use based on the ID code signal received by its receiver, and transmits a confirmation code signal having the identical code signal from its transmitter at a constant intensity.
If a distance between the relative two units are within a specified distance, the use restriction release unit is enabled to receive a signal from the ID signal transmission unit representing that the ID signal transmission unit has detected that the ID code signal received is its own. Upon receipt of this signal, the use restriction release unit transmits a confirmation code signal back to the ID signal transmission unit, and sends a use restriction release signal to an information processing apparatus. On the other hand, if a distance between the two units is more than the specified distance and thus a level of the signal to one unit from the other becomes lower than a predetermined level in the respective units, the use restriction release unit stops the transmission of the use restriction release signal.
Thus, if the distance between the relative two units is within the specified distance, the use restriction of the applicable device is released, while the use restriction becomes to function if the distance becomes more than the specified value.
In a device use restriction system using such an RFID module, the use restriction can be released as long as the RFID module resides within a range of a prespecified distance from a reader/writer provided in the applicable devices.
Herein, a problem is an area where the use restriction of the applicable device is released. If the area is too narrow, the use of the applicable device is forbidden when the user is positioned only a little apart from the applicable device, and thus the usage becomes inconvenient. On the contrary, if the area becomes too large, the use restriction can be released despite the situation that the user is far apart from the applicable device, and thus a fear of being used by unspecified persons arises.